Method and apparatus for monitoring the approach of birth



H. L. EVANS Sept. 20, 1966 METHOD AND APPARATUS FOR MONITORING THEAPPROACH OF BIRTH Filed Aug. 28, 1965 R Z 0 8% M J 4 %06 R W %IIMMMT$ ki m z "KL M M T:

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United States Patent 3,273,559 METHOD AND APPARATUS FOR MONITORING THEAPPROACH OF BIRTH Henry Lee Evans, Ann Arbor, Micln, assignor toConductron Corporation, Ann Arbor, Mich, a corporation of Delaware FiledAug. 28, 1963, Ser. No. 305,149 7 Claims. (Cl. 128-2) This inventionrelates to a monitoring device and has more particularly to do with adevice for monitoring the dilatation of the female cervix during laborand just prior to the actual birth of an infant. The device is soarranged that it eliminates the necessity for the attending physicianmaking personal manual examination of the dilatation from time to time.Thus, it assists materially in contributing to the comfort of the motherduring the final hours of labor and also provides a continuousindication of dilatation which assists in the avoidance of complicationsassociated with precipitous birth that may occur during the time betweenthe examinations by the physiclan.

It is common practice in the treatment of expectant mothers to judge thetime of birth by the so-called expan sion or dilatation of the cervixand the present invention relates to a measuring means which can,without discomfort to the patient, be observed in a suitable instrumentnear the patient.

It is a further object to provide a means for suitably mountingmonitoring devices which requires a minimum of equipment and discomfortto the patient.

Other objects and features of the invention relating to details ofconstruction and operation will be apparent in the following descriptionand claims.

Drawings accompany the disclosure and the various views thereof may bebriefly described as:

FIGURE 1 illustrates a circuit diagram in block form showing the variouselements of the apparatus.

FIGURE 2 illustrates the monitoring elements.

FIGURE 3 is a view showing the manner in which the monitoring elementsare mounted on the lips of the cervix.

FIGURE 4 is a sectional view of the mounting clip taken on line 4-4 ofFIGURE 5.

FIGURE 5 is a sectional view -of a mounting clip taken on line 5-5 ofFIGURE 4.

In the female anatomy, the uterus or womb positioned above the vaginalcavity has a lower half or neck portion which is called the cervix. Thisis the area of the opening of the womb; and, during pregnancy, as childbirth approaches, this opening gradually enlarges or dilates and thedegree of dilatation is indicative of the descent of the child towardthe cervical opening. The womb opening has lip portions referred to atand 12 in FIG- URE 3 in spaced relation, and on these lip portions aremounted expansion clips 14 and 16 having bifurcate gripping portions 18pivoted at 20 with actuating handle portions 22 which are provided withre-entrant curved portions 24 to permit gripping and handling by forcepsshown diagrammatically at 26. The bifurcate gripping portions 18 areprovided with small projections in the form of teeth 28 to insure a firmlocation on the lip of the cervix. The nature of this portion of thebody is such that these clips may be applied without discomfort to thepatient.

A suitable coil spring 30 serves to hold the portions 18 in grippingrelation and these parts are all made of a corrosion resistant materialsuch as stainless steel which can be suitably sterilized. A smallopen-ended cylinder 32 is supported by apertured ears 34 on a transversepivot pin 36 which serves as a pivot for the opposed portions of theclips 14 and and also as a location for the spring 30. The cylinder 32is provided to carry the monitoring devices which form a part of theindicator circuit. These devices can consist of cylindrically shapedcapsules 40 and 42 as shown in FIGURE 2. One capsule 40 can carry whatis called a ferrite load and the dimension of this capsule can beapproximately .5 centimeter in diameter and 1.5 centimeters in length.This ferrite load can be in the nature of a small cylinder of ferritematerial in sintered form, for example, which has the properties offerrite required in the circuit to be described, i.e., a highpermeability or high Q rating. The capsule 42 can contain a miniaturizedHartley oscillator using a transistor as the active element with acoaxial output lead wire 44, this capsule being approximately .5centimeter in diameter and 2 centimeters in length.

The tuned LC tank circuit of the oscillator is the heart of the devicebecause it is in effect the measuring element and it includes anair-wound inductance in capsule 42 and the high permeability or high Qferrite core in capsule 40. The combined inductance of the air core plusthe ferrite determines, in conjunction with a fixed capacitor in thetank circuit, the frequency of oscillation of the Hartley oscillatorcircuit.

The ferrite 49 is attached by clip 14 to one of the cervical lips 10 andthe air core 42 is attached by clip 16 to the other lip 12 as shown inFIGURE 3, the two units being initially adjacent and in close proximitywith one another in the normal undilated condition of the cervix. As thetwo units are separated by dilatation, the inductance of the combinationwill decrease, and the frequency of oscillation will increase. Thechange of frequency in the output signal of the oscillator can bereadily determined as a function of the known displacement of the twounits and a separation indicator can be coupled to the oscillator outputby suitable circuitry as described hereinafter to visually indicate theprogress of the dilatation. The co-axial cable 44 will connect theactive unit 42 inside the mother with the external telemeteringequipment but it will be seen that only the slender coaxial cable 44need extend through the Vagina and that there is no electrical wiringconnection whatsoever between the two elements 40 and 42.

Cable 44 will carry direct current to the transistor and serve as theoutput lead to transmit the oscillator frequency to the counting device.The co-axial cable offers the advantage of a noise shielded signal pathand small size, for example, 2 mms. diameter. It can be covered with aninsert material, such as, for example, rayolin NF, which is stable fromnegative 55 to degrees centigrade, and thus lends itself to easysterilization.

The output of the oscillator is fed to a waveshaping circuit to generatewell-defined zero crossings of the output frequency, and this signalwill in turn drive a monostable multivibrator. The output pulseamplitude will be constant, and the duration of the pulse less than thehighest expected frequency. If the average value of the train of pulsesis determined, it is found to be proportional to the input frequency,and this average value can be displayed on a meter calibrated toindicate displacement.

In FIGURE 1, the ferrite load 40' is shown in spaced relation to theHartley oscillator 42 which is connected by the coaxial cable 44 to awaveshaper 46 having a suitable direct current supply. The waveshaper isconnected to the monostable multivibrator 48 and this is connected to aseparation indicator 50 of a visual nature, such as a needle or a dial.

The units used internally of the patient are preferably mechanicallystabilized by encapsulation in irradiated polyolefin which can be heatshrunk to provide maximum holding of the elements without any volatileglues or solvents. The units will then be dip coated in a heat curablelatex compound to provide a smooth closed cell surface that can beeasily modified to expose the holding attachments and still provide asealed capsule that can be sterilized prior to insertion. The co-axialcable cover also bonds well to latex and as previously indicated, can besterilized. The output cable 44 may have a convenient quick disconnectplug at a suitable location exterior to the patient so that she maydisconnect it from the indicator mechanism and move about if necessary.

What is claimed is:

1. A system for indicating the approach of childbirth in a female mammalcomprising an electrical circuit including first and second elementsphysically and mechanically independent of each other adapted forinsertion in the vaginal cavity of the female and co-operableelectrically with each other to control a measurable parameter of saidcircuit as a function of the proximity of said elements to each other,means associated with said elements adapted to removably attach saidfirst element to one lip of the cervical opening of the female and saidsecond element to the other lip with no physical or mechanicalassociation between the elements, and telemetering means locatedexternally of the female and coupled to said electrical circuit fortranslating varia- :ions in said parameter into a signal for indicatingthe spacing of said cervical lips from each other.

2. A method for monitoring the imminent approach of :hildbirth in afemale mammal comprising the steps of attaching a magnetically permeableelement to one lip 3f the cervical opening of the female, attaching anin- :luctor element to the other lip of said opening, said elernentsbeing physically and mechanically independent of each other, passing anelectrical current through said inductor to generate a magnetic fieldencompassing said :lement in all positions of said lips, and translating:hanges in the inductance of said inductor caused by changes in theproximity of said element to said inductor into an electrical signalindicative of the spacing of said lips from each other.

3. A method for monitoring the imminent approach of childbirth in afemale mammal which comprises the steps of associating, with the spacedlips of the cervix, first and second elements of an electricalinductance :ircuit co-operable with each other but physically detachedfrom each other to control a measurable param- :ter of said circuit as afunction of the proximity of said elements to each other and coupling insaid circuit a telemetering means located externally of the body fortranslating variations in said parameter into a signal for indicatingthe spacing of said cervical lips.

4. An apparatus for indicating the approach of childbirth in a femalemammal which comprises resiliently expandable clamping means forattachment to the opposed cervical lips of the female, means on saidclamping means remotely operable manually to permit attachment anddetachment, first and second elements adapted for insertion into thevaginal cavity carried respectively by said clamping means andphysically independent of each other, an electrical circuitincorporating said elements to create a measurable parameter as afunction of the proximity of said elements to one another, andtelemetering means located externally of the female and coupled to saidelectrical circuit for translating variations in said parameter into asignal for indicating the spacing of said cervical lips from each other.

5. A device as defined in claim 4 in which only one of said elements isphysically connected in said circuit.

6. A device as defined in claim 4 in which each of said elements isencapsulated in a waterproof, relatively inert material to permitsterilization.

'7. A device as defined in claim 4 in which said clamping means eachcomprise jaw-like members pivoted to each other, spring means to biassaid members toward each other, and opposed extensions on said membersto permit manipulation thereof to a proper clamping position.

References Cited by the Examiner UNITED STATES PATENTS 2,239,330 4/1941Lorand 128-2 2,652,825 9/1953 Rauh 128Z 2,831,478 4/1958 Uddenberg 12822,824,220 2/1960 Von Micsky l28361 FOREIGN PATENTS 17,220 9/1900 GreatBritain.

RICHARD A. GAUDET, Primary Examiner.

LOUIS R. PRINCE, Examiner.

S. BRODER, Assistant Examiner.

1. A SYSTEM FOR INDICATING THE APPROACH OF CHILDBIRTH IN A FEMALE MAMMALCOMPRISING AN ELECTRICAL CIRCUIT INCLUDING FIRST AND SECOND ELEMENTSPHYSICALLY AND MECHANICALLY INDEPENDENT OF EACH OTHER FOR INSERTION INTHE VAGINAL CAVITY OF THE FEMALE AND CO-OPERABLE ELECTRICALLY WITH EACHOTHER TO CONTROL A MEASURABLE PARAMETER OF SUCH CIRCUIT AS A FUNCTION OFTHE PROXIMITY OF SAID ELEMENTS TO EACH OTHER, MEANS ASSOCIATED WITH SAIDELEMENTS ADAPTED TO REMOVABLY ATTACH SAID FIRST ELEMENT TO ONE LIP OFTHE CERVICAL OPENING OF THE FEMALE AND SAID SECOND ELEMENT TO THE OTHERLIP WITH NO PHYSICAL OR MECHANICAL ASSOCIATION BETWEEN THE ELEMENTS, ANDTELEMETERING MEANS LOCATED EXTERNALLY OF THE FEMALE AND COUPLED TO SAIDELECTRICAL CIRCUIT FOR TRANSLATING VARIATIONS IN SAID PARAMETER INTO ASIGNAL FOR INDICATING THE SPACING OF SAID CERVICAL LIPS FROM EACH OTHER.